how to water your plants from afar

Now I know what you're thinking and you're right, I live in England, it rains here all of the time why would I ever bother watering? But tomato plants are needy little things, so I want to leave them with an extra boost of water while we are in Wales next week. All you need is a plastic bottle, a nail and a hammer to poke a hole through the cap and you've got yourself an automatic water drip.